The present invention relates to a method for producing woven air bags, particularly multi-ply at least in part, as well as to a fabric, particularly for air bags multi-ply in part.
After weaving, fabrics, especially for partly multi-ply air bags, are as a rule cut to size on patterning tables. Air bags configured multi-ply in part as woven in once piece on weaving machines are termed “one-piece-woven” (OPW) air bags. The ply and contour of the OPW air bag in the web of fabric coming from the weaving machine are intended as specifications for a cutting system.
Air bag fabrics currently employed, especially for OPW air bags, including air bags woven multi-ply contoured make it very difficult to adapt an action to the discrete contour of the air bag in the fabric. Although for the sake of simplicity the term OPW is used throughout the following description, it is understood that this includes air bag fabrics, woven air bags and OPW air bags. The woven single-ply contour hardly stands out, for example, from woven two-ply portions, resulting in it failing to be reliably “seen” by automatic sensing systems.
In OPW patterning this poses the following problems. In current air bag fabric patterning systems single or sets of blanks materialize as follows: from cutting system specifications for dimensioning discrete parts a program sequence is generated manually or automatically e.g. via a CAD program for a CNC cutter, for example, which describes how the discrete parts are to be cut from the air bag fabric. Cutting is done irrespective of the status of the fabric each time, i.e. the cutter moves relative to a fiducial of the cutting system no matter how and where the fabric is actually located in the system. This means that any deviations in the fabric, especially as regards dimensions of the OPW fail to be automatically taken into account or corrections make manually intervention in the program sequence necessary. This, as a rule, involves halting the machine with serious disadvantages in time and money in making the correction and possibly resulting in a high percentage of rejects in continuation of the program (possibly incorrect). This is why, especially with OPW air bags the reject percentage is high because of deviations dimensionally in the various parts of the fabric as is especially the case with articles having extremely critical contours due to the weaving contour being infringed or nicks in the air bag chamber or the tolerances of the cutting edge relative to the woven contours being exceeded or fallen short of.
In the online gaging systems as used in the aforementioned patterning systems, implementing gaging on unblanked OPWs in the air bag fabric at defined locations lacks reliability because the woven contours cannot be reliably sensed. Establishing the values necessitates manual gaging at considerable cost and manual expenditure.
The present invention is based on the objective of proposing a method for producing air bags woven particularly multi-ply at least in part, as well as a fabric, in avoiding or at least greatly diminishing the disadvantages of prior art. This objective is achieved, for one thing, by a method as it reads from claim 1 and, for another, by a fabric as it reads from claim 2. The method in accordance with the invention comprises the following steps:                a) preparing the warp threads in the warping shop so that warp threads suitable as machine-readable marker threads are already included in the warp,        b) weaving the air bag fabric so that weft threads suitable as machine readable marker threads are included in the weave of at least part of the cloth width,        c) cutting out the air bag from the air bag fabric by means of a cutter guided by said machine-readable threads included in the weave.        
This method has the major advantage that the incorporated markers now ensure that the resulting fiducials in the fabric are machine-readable and always reliably attained in the subsequent steps in the process. This method permitting any desired position and number of markers now makes it possible to correct any deviations in contour and dimensions in and between the discrete air bags located in the woven web on patterning and in addition to reliably place fiducials in subsequent steps in the process, now irrespective of the fact that a textile is live and each variation of the air bag makes for different requirements.
The fabric in accordance with the invention, especially for air bags woven multi-ply in part, is characterized by machine-readable markers for sensing specific portions of the fabric. In this arrangement the markers, for example single or multiple threads differing in color, structure, material or in some other way from the air bag fabric as so-called marker threads or other linear or non-linear or dotted markers are included in the weave or otherwise incorporated before, during or after the weaving process. These marker threads or markers now make it possible to advantage via defined wanted spacings to each other and the defined wanted arrangement relative to a OPW in conjunction with each of the actual spacings and actual arrangement to gage the shape and/or size and/or orientation or distortion of the patterned OPW or OPW in the uncut air bag fabric or of the blank following cutting in subsequent steps in the method. Further advantages and features of the invention read from the sub-claims.